In recent years, liquid crystal display devices have come to be widely used in smartphones, personal digital assistants (PDAs), tablet computers, satellite navigation systems, etc. In general, a liquid crystal display device comprises a liquid crystal display panel and a surface illumination device (backlight device) which is overlaid on the rear surface of the liquid crystal display panel and illuminates the liquid crystal display panel. Conventional backlight devices include a reflective layer, a lightguide plate (lightguide), an optical sheet, light emitting diodes (LEDs) as light sources, and a rectangular frame formed of resin. The reflective layer, the lightguide plate, and the optical sheet are stacked on each other, and disposed in the frame. The reflective layer, the lightguide plate, and the optical sheet are thereby supported and positioned by the frame.
Furthermore, there has been proposed a structure in which a frame is engaged in a container formed of a metal plate (backlight cover), and the reflective layer, lightguide plate, and optical sheet are arranged inside a hollow part of the frame.
In recent years, as display areas have increased, there has been a continual demand for the frames of liquid crystal display devices to become ever narrower and the liquid crystal display devices to become ever thinner. However, the dimensions such as width, thickness, etc., of the frame in the above-described backlight device is approaching the structural limit of injection molding, and such a demand is difficult to achieve.
Furthermore, a tolerance between an effective illumination area of the backlight device and a liquid crystal display effective area has become smaller. Thus, when the backlight device is attached to a liquid crystal display device, the liquid crystal display effective area shifts to the outside of the effective illumination area, and the display quality may decrease.